Sheet processing apparatus and image forming system

Abstract

A sheet processing apparatus includes a pair of clamp units, a first pressing unit and a second pressing unit. The first pressing unit performs a square back process on a spine of the sheet bundle by moving the first pressing unit in a width direction of the sheet bundle in a state in which the spine of the sheet bundle is pressed toward the pair of clamp units. The second pressing unit performs a pressing process on a folding line of the sheet bundle by moving in the width direction of the sheet bundle while nipping the folding line of the sheet bundle.

What is claimed is: 
     
         1 . A sheet processing apparatus comprising:
 a conveyance portion configured to convey a sheet bundle subjected to a half-folding process or the sheet bundle subjected to a saddle binding process and the half-folding process such that a spine of the sheet bundle is positioned downstream of a fore edge thereof in a conveyance direction in which the conveyance portion conveys the sheet bundle;   a pair of clamp units configured to clamp the sheet bundle;   a first pressing unit configured to press, toward the pair of clamp units, the spine of the sheet bundle protruding downstream in the conveyance direction with respect to the pair of clamp units in a state in which the sheet bundle is clamped by the pair of clamp units, so as to perform a square back process on the spine of the sheet bundle by moving the first pressing unit in a width direction of the sheet bundle in a state in which the spine of the sheet bundle is pressed toward the pair of clamp units; and   a second pressing unit configured to perform a pressing process on a folding line of the sheet bundle by moving in the width direction of the sheet bundle while nipping the folding line of the sheet bundle.   
     
     
         2 . The sheet processing apparatus according to  claim 1 , wherein a protrusion amount of the sheet bundle from a downstream end surface of the pair of clamp units in the conveyance direction in a case of performing the pressing process by the second pressing unit is larger than a protrusion amount of the sheet bundle from the downstream end surface of the pair of clamp units in the conveyance direction in a case of performing the square back process. 
     
     
         3 . The sheet processing apparatus according to  claim 2 ,
 wherein the first pressing unit includes a pressing roller configured to press the spine of the sheet bundle,   wherein the second pressing unit includes a pair of folding reinforcement rollers configured to nip the folding line of the sheet bundle, and   wherein an upstream end portion of a nip of the pair of folding reinforcement rollers in the conveyance direction is positioned downstream of a position where a surface of the pressing roller comes into contact with the spine of the sheet bundle in the square back process in the conveyance direction.   
     
     
         4 . The sheet processing apparatus according to  claim 1 , wherein a nipping pressure by which the pair of clamp units nip the sheet bundle in a case of performing the square back process is higher than the nipping pressure by which the pair of clamp units nip the sheet bundle in a case of performing the pressing process by the second pressing unit. 
     
     
         5 . The sheet processing apparatus according to  claim 4 ,
 wherein the pair of clamp units include a first urging portion and a second urging portion for generating the nipping pressure for nipping the sheet bundle,   wherein the nipping pressure is generated by the first urging portion in the case of performing the pressing process by the second pressing unit, and   wherein the nipping pressure is generated by the first urging portion and the second urging portion in the case of performing the square back process.   
     
     
         6 . The sheet processing apparatus according to  claim 1 , further comprising:
 a coupling mechanism configured to couple the first pressing unit and the second pressing unit to each other; and   a drive source configured to move the first pressing unit and the second pressing unit coupled to each other by the coupling mechanism in the width direction of the sheet bundle.   
     
     
         7 . The sheet processing apparatus according to  claim 6 , wherein the drive source moves the first pressing unit and the second pressing unit in the width direction of the sheet bundle in a case where the second pressing unit is moved in the width direction of the sheet bundle and the first pressing unit is coupled to the second pressing unit by the coupling mechanism. 
     
     
         8 . The sheet processing apparatus according to  claim 1 ,
 wherein the pair of clamp units includes a pair of first clamp portions and a pair of second clamp portions positioned downstream of the pair of first clamp portions in the conveyance direction,   wherein the sheet bundle is nipped by the pair of first clamp portions and the pair of second clamp portions in a case of performing the square back process, and   wherein the sheet bundle is nipped by the pair of first clamp portions and not nipped by the pair of second clamp portions in a case of performing the pressing process by the second pressing unit.   
     
     
         9 . The sheet processing apparatus according to  claim 1 ,
 wherein the pair of clamp units include a pair of first clamp portions and a pair of second clamp portions positioned downstream of the pair of first clamp portions in the conveyance direction,   wherein the sheet bundle is nipped by the pair of first clamp portions and the pair of second clamp portions in a case of performing the square back process, and   wherein, in a case of performing the pressing process by the second pressing unit, the sheet bundle is nipped by the pair of first clamp portions and the pair of second clamp portions, and a nipping pressure for nipping the sheet bundle by the pair of second clamp portions is lower than in the case of the square back process.   
     
     
         10 . The sheet processing apparatus according to  claim 8 ,
 wherein a protrusion amount of the sheet bundle from a downstream end surface of the pair of clamp units in the conveyance direction in a case of performing the pressing process by the second pressing unit is larger than a protrusion amount of the sheet bundle from the downstream end surface of the pair of clamp units in the conveyance direction in a case of performing the square back process, and   wherein the downstream end surface of the pair of clamp units in the conveyance direction is a downstream end surface of the pair of second clamp portions in the conveyance direction.   
     
     
         11 . The sheet processing apparatus according to  claim 1 ,
 wherein one clamp unit among the pair of clamp units includes a fixed clamp portion configured not to move in a case of performing the pressing process by the second pressing unit and in a case of performing the square back process,   wherein another clamp unit among the pair of clamp units includes
 a movable member movable to a first position and a second position closer to the one clamp unit than the first position, 
   a movable clamp portion provided to be movable in a thickness direction of the sheet bundle with respect to the movable member,   a first spring disposed between the movable member and the movable clamp portion, and   a second spring that is disposed between the movable member and the movable clamp portion and that is shorter than the first spring,   wherein in the case of performing the pressing process by the second pressing unit, the first spring is compressed between the movable member and the movable clamp portion by moving the movable member to the first position and nipping the sheet bundle by the fixed clamp portion and the movable clamp portion, and   wherein in the case of performing the square back process, the first spring and the second spring are compressed between the movable member and the movable clamp portion by moving the movable member to the second position and nipping the sheet bundle by the fixed clamp portion and the movable clamp portion.   
     
     
         12 . The sheet processing apparatus according to  claim 11 ,
 wherein a protrusion amount of the sheet bundle from a downstream end surface of the pair of clamp units in the conveyance direction in the case of performing the pressing process by the second pressing unit is larger than a protrusion amount of the sheet bundle from the downstream end surface of the pair of clamp units in the conveyance direction in the case of performing the square back process, and   wherein the downstream end surface of the pair of clamp units in the conveyance direction is a downstream end surface of the fixed clamp portion and the movable clamp portion in the conveyance direction.   
     
     
         13 . An image forming system comprising:
 an image forming unit including an image forming portion configured to form an image on a sheet; and   a sheet processing apparatus configured to perform a pressing process on a sheet bundle subjected to a half-folding process or the sheet bundle subjected to a saddle binding process and the half-folding process and perform a square back process on the sheet bundle subjected to the saddle binding process and the half-folding process, the sheet bundle being formed from sheets on which images have been formed by the image forming portion,   wherein the sheet processing apparatus includes
 a conveyance portion configured to convey the sheet bundle subjected to the half-folding process or the sheet bundle subjected to the saddle binding process and the half-folding process such that a spine of the sheet bundle is positioned downstream of a fore edge thereof in a conveyance direction in which the conveyance portion conveys the sheet bundle, 
   a pair of clamp units configured to clamp the sheet bundle,   a first pressing unit configured to press, toward the pair of clamp units, the spine of the sheet bundle protruding downstream in the conveyance direction with respect to the pair of clamp units in a state in which the sheet bundle is clamped by the pair of clamp units, so as to perform the square back process on the spine of the sheet bundle by moving the first pressing unit in a width direction of the sheet bundle in a state in which the spine of the sheet bundle is pressed toward the pair of clamp units, and   a second pressing unit configured to perform the pressing process on a folding line of the sheet bundle by moving in the width direction of the sheet bundle while nipping the folding line of the sheet bundle.